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TETRA - Direct Mode Operation

TETRA - Direct Mode Operation. Doug Gray Motorola. AGENDA. Introduction & explanation of Direct Mode Operation (DMO) Services & Facilities Benefits & Applications Conclusions. DMO. WHY DIRECT MODE IN TRUNKING?.

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TETRA - Direct Mode Operation

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  1. TETRA - Direct Mode Operation Doug Gray Motorola

  2. AGENDA • Introduction & explanation of Direct Mode Operation (DMO) • Services & Facilities • Benefits & Applications • Conclusions

  3. DMO WHY DIRECT MODE IN TRUNKING? • Trunking offered many benefits over conventional communications and was a great success in the market • It missed a key feature that conventional communications offered - direct communication outside network coverage Automatic Operation Spectral Efficiency ? • TETRA’s multi-mode capability offers the best of both worlds - Trunking and Direct Communications in a single terminal. Ease of Data Services Feature Rich Service

  4. WHAT IS TETRA DIRECT MODE ? • There are 4basic operational modes of TETRA DMO, viz. 1 “Back-to-back”(standard DMO terminal coverage) 2 DMO Repeater(extended DMO terminal coverage) 3 Dual Watch (periodic “scanning” of ‘other’ mode) 4 DMO Gateway(continuous relay between modes) • Communication between Direct Mode terminals • Communication between trunked and DMO terminals • Further permutations are possible, e.g. Gateway/Repeater

  5. TETRA DMO - BACK-TO-BACK C TRUNKED TETRA TETRA DMO A1 TETRA DMO B1 A3 A2 B2 B3

  6. TETRA DMO REPEATER A1 C TRUNKED TETRA A3 DMO Repeater B1 TETRA DMO DMO Repeater B2 TETRA DMO B3 A2

  7. TETRA DMO-DUAL WATCH A1 TETRA DMO C TRUNKED TETRA TETRA DMO A3 A2 Dual-Watch B1 B2 Dual-Watch B3

  8. TETRA DMO - GATEWAY A1 TETRA DMO C TRUNKED TETRA TETRA DMO A3 Gateway B1 Gateway B3

  9. 1 1 2 2 3 3 4 4 DMO Air Interface ‘Frequency Efficient’ mode can use these timeslots for another call Pre-emption Speech Slot ‘BACK-TO-BACK’ DMO Slot Structure DMO DMO Master Slave

  10. DMO CHARACTERISTICS • Normal DMO enables 1 conversation per carrier(i.e. 1 per 4 timeslots) • Transmitting radio acts as ‘Master’ on a single timeslot • Receiving radio is ‘Slave’ on a single timeslot • In normal mode, two time slots are used, two are free • In Frequency Efficient Mode, all four timeslots are used (2x2) enabling two conversations per carrier

  11. TYPE 1A DM1 MS RX MS TX • Single carrier (1A) • Simple RF • 1 conversation, 1 DM channel • Single carrier • Dual carrier (1B) • More complex RF • 1 conversation, 2 DM channels • Supports multiple repeaters • Reduces potential for RF interference TYPE 1B DM1 DM2 MS RX MS TX DMO REPEATER TYPE 1A & 1B • Only one call per repeater • Uses a 4 slot structure • 2 slot uplink • 2 slot downlink • Master/slave operation (3 slot delay)

  12. 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 DMO Air Interface Frequency Usage DM1 Master Slot MS RX 1 2 3 4 Slave Slot SPEECH DOWNSLOT SPEECH UPSLOT Pre-Emption Upslot Direct Mode Channel DM1 Direct Mode Channel DM1 DMO DMO Master Slave (Slave slot pattern moved for diagram clarity) DMO REPEATER TYPE 1A Type 1A Repeater

  13. TYPE 2 DM1 DM2 RPT RX RPT TX DMO REPEATER TYPE 2 • Two simultaneous calls per repeater • Uses a 4 slot structure • 4 slot uplink • 4 slot downlink • Master/slave operation (4 slot delay) • Dual carrier • More complex RF but supports multiple repeaters • Uses power control and addressing

  14. 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 ‘B’ channel can use other slots DMO Air Interface Uplink Carrier 1 2 3 4 Downlink Carrier SPEECH DOWNSLOT SPEECH UPSLOT Pre-Emption Upslot Direct Mode Channel DM1 Direct Mode Channel DM2 DMO DMO Master Slave (Slave slot pattern omitted for diagram clarity) DMO REPEATER TYPE 2 Type 2 Repeater

  15. Mobile Unit whilst engaged in a call in Trunking mode is alerted of a DMO call/request from a DMO terminal. DUAL WATCH • Radio is operational in one system mode (Direct or Trunked) and simultaneously monitors signalling on the other system.

  16. Frequency Usage TM1 TM2 DM1 Trunked Mode Air Interface GW RX GW TX DMO User DMO GATEWAY • Enables DMO terminal to communicate with the trunking system & vice versa • Uses ‘normal’ DMO air interface(single call) 'Normal' DMO Air Interface (One simultaneous call) Uplink (TM1) Downlink (TM2) Gateway Direct Mode Channel DM1 • One DMO carrier per call Trunked Mode Cell

  17. Frequency Usage TM1 TM2 DM1 Trunked Mode Air Interface GW RX GW TX DMO REPEATER/GATEWAY • Combines the functionality of a repeater and a gateway (similar to a VHF-UHF talk-through repeater) • Interconnects direct mode to trunked mode • Uses ‘normal’ DMO air interface (single call) • Can be manned or stand alone (i.e. free running or manned by an operator)

  18. BENEFITS of DMO GATEWAY • Extends range of Trunking Mode Operation • Reduces Infrastructure costs • Enables remote ‘occasional users’ to have communication at cost effective rates • Gives Network Operators better coverage possibilities during early stages of network roll-out

  19. MDMO terminal is restricted from transmitting unlessit receives an authorising signal O.K. DMO MANAGED DIRECT MODE - MDMO • Generated by authorising device which is in permanent contact with system, or….. • …. generated by modified DMO Gateway or Repeater/Gateway device • Validity time encoded in authorising signal

  20. BENEFITS OF MDMO • Network Operators maintain better control of their network resource/ revenues • Removes potential for interference • Manages roaming

  21. DMO SERVICES AND FACILITIES • Simplex speech - Individual or Group Call • Circuit mode data up to 7.2 kbps, incl. point-to-point & point-to-multipoint • Status and short data service (SDS) • Late Entry • Emergency call • Talking Party Identification (TPI) , incl. concealment

  22. DMO SECURITY (ENCRYPTION) • Air-interface encryption - TEA1, TEA2 & TEA3, incl. time stamping • Implicit authentication • Key management incl. Over The Air Rekeying (OTAR) • “Zapping” (enabling/ disabling) terminals • End-to-end encryption mechanism

  23. DMO BENEFITS & APPLICATIONS • Operation outside the coverage of Trunking Infrastructure • Gives extra capacity when trunked network is highly loaded • Operations in poor signal strength areas • Fall-back operation when the Trunking Infrastructure system is inoperative • Covert Operations - cannot be monitored by Contol • ‘Stripline’ applications (power, oil, water distribution lines) not requiring trunked network capacity

  24. CONCLUSIONS • TETRA is a multi-modestandard offering trunking and conventional operation in-one • DMO - a powerful feature in the total TETRA offering, as it comprises of several sub-modes of operation • Significant commonality with trunked V+D TETRA enables for multi-mode terminals (DMO & V+D) • DMO is a significant differentiator between TETRA and other cellular services

  25. TETRA - Direct Mode Operation Thank You Doug Gray Motorola

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